Exposure unit with staggered LED arrays

Abstract

The image reproduction system includes a light exposure unit and a photosensitive member having an outer surface. The exposure unit includes a staggered plurality of linear LED arrays and a staggered plurality of discrete objectives associated therewith which focus the light generated by the LED arrays on the outer surface of the photosensitive member.

What is claimed is:  
     
       1. An image reproduction system comprising: 
       a photosensitive member having an outer surface;  
       a staggered plurality of linear light emitting diode (“LED”) arrays, said LED arrays being staggered such that each LED array is spaced from an imaginary plane perpendicular to the process direction of said image reproduction system; and  
       a staggered plurality of discrete objectives for focussing the outputs of said LED arrays on said outer surface of said photosensitive member, each of said objectives being associated with a LED array, said objectives being oriented substantially parallel to said outer surface and positioned between said photosensitive member and said staggered plurality of linear LED arrays such that the distance from each objective to said imaginary plane is from 40% to 60% of the distance from its associated LED array to said imaginary plane.  
     
     
       2. The system of  claim 1 , further comprising an opaque screen mounted between said staggered plurality of discrete objectives and said outer surface of said photosensitive member, said opaque screen having a slit through which the focussed outputs of said LED arrays are projected on said outer surface of said photosensitive member. 
     
     
       3. The system of  claim 1 , wherein said objectives are optically aligned such that they focus the outputs of their associated LED arrays on a common line on said outer surface of said photosensitive member. 
     
     
       4. The system of  claim 1 , wherein said objectives are thermally connected to a holder and said LED arrays are thermally connected to a carrier, wherein a cooler is provided to actively cool said carrier and said holder. 
     
     
       5. The system of  claim 4 , wherein said holder and said carrier are thermally connected to each other. 
     
     
       6. The system of  claim 4 , wherein said holder and said carrier are substantially composed of a material with a coefficient of linear expansion of 5×10 −6  per K or below. 
     
     
       7. The system of  claim 1 , wherein the length of each LED array is selected such that when put on one line, at least two adjacent LED arrays are partially overlapping. 
     
     
       8. The system of  claim 7 , wherein said staggered plurality of objectives is positioned such that the aspect ratio between the image and the projected image is substantially 1:1. 
     
     
       9. The system of  claim 1 , further comprising a plurality of non-reflective opaque screens positioned between said staggered plurality of linear LED arrays and said staggered plurality of objectives, each of said screens being positioned both between two neighbouring LED arrays and the associated objectives. 
     
     
       10. A method of creating a latent image reproduction, said method comprising: 
       concurrently emitting bands of light from a staggered plurality of light emitting diodes (“LED”), each band including information indicative of a portion of a line of an image to be reproduced;  
       focussing said bands through a staggered plurality of discrete objectives onto an outer surface of a photosensitive member, each of said staggered plurality of LED arrays being associated with one of said staggered plurality of discrete objectives; and  
       overlapping a part of said focussed bands to form a common line on said outer surface of said photosensitive member, said common line including information indicative of said line of said image.  
     
     
       11. The method of  claim 10 , further comprising orienting said staggered plurality of discrete objectives to be substantially parallel to said outer surface and positioned between said photosensitive member and said staggered plurality of LED arrays. 
     
     
       12. The method of  claim 11 , further comprising spacing each of said staggered plurality of LED arrays at a first distance from an imaginary plane perpendicular to a process direction of said latent image reproduction. 
     
     
       13. The method of  claim 12 , further comprising spacing each of said staggered plurality of discrete objectives at a second distance from said imaginary plane perpendicular to said process direction of said latent image reproduction. 
     
     
       14. The method of  claim 13 , wherein said second distance is less than said first distance for each of said staggered plurality of LED arrays and its associated one of said staggered plurality of discrete objectives. 
     
     
       15. The method of  claim 14 , wherein said second distance is between 40% and 60% of said first distance. 
     
     
       16. The method of  claim 10 , further comprising arranging said staggered plurality of LED arrays such that when put on one line adjacent LED arrays partially overlap. 
     
     
       17. The method of  claim 16 , further comprising positioning said staggered plurality of discrete objectives such that an aspect ratio between said line of said image and said common line of said latent image reproduction is substantially 1:1. 
     
     
       18. The method of  claim 10 , further comprising optically aligning each of said staggered plurality of discrete objectives to focus the output of its associated one of said staggered plurality of LED arrays onto said common line. 
     
     
       19. The method of  claim 10 , further comprising cooling said staggered plurality of discrete objectives and said staggered plurality of LED arrays to maintain their relative alignment to one another. 
     
     
       20. An image reproduction system comprising: 
       a photosensitive member having an outer surface;  
       a staggered plurality of linear light emitting diode (“LED”) arrays configured for concurrent activation, said LED arrays being staggered such that each LED array is spaced from an imaginary plane perpendicular to the process direction of said image reproduction system; and  
       a staggered plurality of discrete objectives for focussing the outputs of said LED arrays on said outer surface of said photosensitive member, each of said objectives being associated with a LED array, said objectives being oriented substantially parallel to said outer surface and positioned between said photosensitive member and said staggered plurality of linear LED arrays such that the distance from each objective to said imaginary plane is from 40% to 60% of the distance from its associated LED array to said imaginary plane.  
     
     
       21. A system for creating a latent image reproduction, said system comprising: 
       means for concurrently emitting bands of light, each band including information indicative of a portion of a line of an image to be reproduced;  
       means for focussing said bands onto an outer surface of a photosensitive member; and  
       means for overlapping a part of said focussed bands to form a common line on said outer surface of said photosensitive member, said common line including information indicative of said line of said image.